The present invention relates to prosthetic devices and more particularly to an improved liner for prosthetic devices including artificial limbs that also may be articulable or bionic.
An amputee is a person who has lost part of an extremity or limb such a leg or arm which commonly may be termed as a residual limb. Residual limbs come in various sizes and shapes with respect to the stump. That is, most new amputations are either slightly bulbous or cylindrical in shape while older amputations that may have had a lot of atrophy are generally more conical in shape. Residual limbs may further be characterized by their various individual problems or configurations including the volume and shape of a stump and possible scar, skin graft, bony prominence, uneven limb volume, neuroma, pain, edema or soft tissue configurations.
Referring to FIGS. 1 and 2, a below the knee residual limb 10 is shown and described as a leg 12 having been severed below the knee terminating in a stump 14. In this case, the residual limb 10 includes soft tissue as well as the femur 16, knee joint 18, and severed tibia 20 and fibula 22. Along these bone structures surrounded by soft tissue are nerve bundles and vascular routes which must be protected against external pressure to avoid neuromas, numbness and discomfort as well as other kinds of problems. A below the knee residual limb 10 has its stump 14 generally characterized as being a more bony structure while an above the knee residual limb may be characterized as including more soft tissue as well as the vascular routes and nerve bundles.
Referring to FIG. 3, amputees who have lost a part of their arm 26, which terminates in a stump 28 also may be characterized as having vascular routes, nerve bundles as well as soft and bony tissues. The residual limb 10 includes the humerus bone 30 which extends from below the shoulder to the elbow from which the radius 34 and ulna 36 bones may pivotally extend to the point of severance. Along the humerus bone 30 are the biceps muscle 38 and the triceps muscle 40 which still yet may be connected to the radius 34 and the ulna 36, respectively.
In some respects, the residual limb amputee that has a severed arm 26 does not have the pressure bearing considerations for an artificial limb but rather is concerned with having an artificial limb that is articulable to offer functions typical of a full arm, such as bending at the elbow and grasping capabilities. An individual who has a paralyzed limb would also have similar considerations wherein he or she would desire the paralyzed limb to have some degree of mobility and thus functionality.
Historically, artificial limbs typically used by a leg amputee were for the most part all made out wood such an Upland Willow. The limbs were hand carved with sockets for receiving the stump 14 of the residual limb 10. Below the socket would be the shin portion with the foot below the shin. These wooden artificial limbs were covered with rawhide which often were painted. The sockets of most wood limbs were hollow as the limbs were typically supported in the artificial limb by the circumferential tissue adjacent the stump 14 rather than at the distil end of the stump 14.
Some artificial limbs in Europe were also made from forged pieces of metal that were hollow. Fiber artificial limbs were also used which were stretched around a mold afterwhich they were permitted to dry and cure. Again, these artificial limbs were hollow and pretty much supported the residual limb about the circumferential tissue adjacent the stump 14.
All of these various artificial limbs have sockets to put the amputee's stump 28 thereinto. There are generally two categories of sockets. There are hard sockets wherein the stump goes right into the socket actually touching the socket wall without any type of liner or stump sock. Another category of sockets is a socket that utilizes a liner or insert. Both categories of sockets typically were opened ended sockets were they had a hollow chamber in the bottom and no portion of the socket touched the distil end of the stump 14. So, the stump was supported about its circumferential sides as it fits against the inside wall of the sockets.
These types of sockets caused a lot of shear force on the stump 14 as well as had pressure or restriction problems on the nerve bundles and vascular flow of fluid by way of the circumferential pressure effect of the socket on the limb. This pressure effect could cause a swelling into the ends of the socket where an amputee may develop severe edema and draining nodules at the end of their stump 14.
With time, prosthetists learned that by filling in the socket's hollow chamber and encouraging a more total contact with the stump and the socket, the swelling and edema problems could be eliminated. However, the problematic tissue configurations, such as bony prominences, required special consideration such as the addition of soft or pliable materials to be put into the socket.
Today, most artificial limbs are constructed from thermoset plastics such a polyester resins, acrylic resins, polypropylenes and polyethylenes, which are perhaps laminated over a nylon stockinette which also may be impregnated by the various resins.
In the past, most artificial limbs were suspended from the amputee's body by some form of pulley, belt or strap suspension often used with various harnesses and perhaps leather lacers or lacings. Another method of suspending artificial limbs is known as the wedge suspension wherein an actual wedge is built into the socket which is more closed at its top opening. The wedge in the socket cups the medial femoral condyle or knuckle at the abductor tubical. Yet another form of suspension is referred to as the shuttle system or a mechanical hookup or linkup wherein a thin suction liner is donned over the stump that has a docking device on the distal end which mechanically links up with its cooperative part in the bottom of the socket chamber. Sleeve suspensions were also used wherein the amputee may use a latex rubber tube which forms into a rubber-like sleeve which would be rolled on over both the top of the artificial limb and onto the amputee's thigh. The sleeve suspensions have been used in combination with other forms of suspension techniques.
The first artificial limb socket liners were made with molded horsehide leather covered with strips from extruded sheets of rubber glued to the leather as the liner was built up over a positive cast of the residual limb. As before, stump socks typically made of cotton or wool were used with these first liners as well as with the earlier hard sockets.
The next major socket liner was formed from an expanded foam such as polyurethane foam as sold by Durr-Fillauer Medical, Inc. of Chatanooga, Tenn. After a positive cast was made of the residual limb, a cone-like structure of the hard foam plastic was formed and heated. Next, the expanded foam was pulled over the cast of the residual limb in an effort to form it to the limb after which the foam was cooled and its shape was retained over the positive cast. Thereafter, a hard shell socket could be built or laminated over the liner from which a shin and foot of the artificial limb could be attached.
Another type of socket liner was made from a combination of silicone and gauze being sandwiched in between two pieces of leather. However, this type of liner had problems in that it was much too rigid, wouldn't stretch and eventually loosened up and migrated thereby becoming ineffective.
The next group of socket liners were made from the impregnation of a cotton stockinette with silicone resins formed over a positive cast of the residual limb. The problem with these types of liners is that the silicone could not migrate or stretch and was often short lived in that sweat from the residual limb would break down the silicone and create pungent and unsanitary conditions.
Another type of silicone liner without the impregnated stockinette has been utilized to create suction about the residual limb for use in combination with perhaps a shuttle or mechanical link up device with the socket. However, these types of liners offered no yield or cushion and required the wearing of stump socks.
While some of these devices addressed some of the problems associated with prosthetics, none of the artificial limbs, liners and sockets, individually or in combination offered a prosthesis that presented a total contact relationship with the residual limb; absorbed and dissipated shear, shock and mechanical forces transmitted to the limb tissues by the artificial limb; controlled perspiration of the residual limb; controlled residual limb volume; and, promoted equal weight distribution while having a long life expectancy.
There is a need for a liner to be used with prosthetic devices that will offer total contact relationship with the residual limb; provide hypobaric suction suspension with a sticky or tacky surface condition; absorb and dissipate shock, mechanical and shear forces typically associated with ambulation, twisting and turning and weight bearing with an artificial limb; control perspiration; control residual limb volume by way of even weight distribution; and offer relief for the various tissue configurations that plague residual limbs while yet being of long life.